Introduction: Trichomonas vaginalis (TV) is a sexually transmitted infection (STI) associated with increased transmission of human immunodeficiency virus (HIV) and significant adverse birth outcomes. Although culture is often used in the diagnosis of TV, molecular diagnosis is rapid, accurate, and data-rich.
Methods Women were recruited from two clinics in South Africa as part of a study assessing point-of-care polymerase chain reaction (PCR) diagnosis and treatment of three STIs. HIV-infected pregnant women were screened for TV using the Xpert TV (Cepheid, Sunnyvale, CA). Each woman who tested TV PCR-positive provided an additional sample for culture (InPouch TV, Biomed, San Jose, CA). We compared TV detection between PCR and culture, and used non-parametric statistics to compare cycle threshold (Ct) values among culture results and treatment outcomes.
Results By December 31st, 2016, 200 women were enrolled and 52 (26%) tested TV PCR-positive. Baseline cultures were obtained from 41 (79%) of the TV PCR-positive women, and 22 (54%) were culture-positive. The median baseline Ct of the TV PCR-positive/culture-positive group was 24.0 (IQR: 5.1) vs. 38.0 (IQR: 3.8) among those TV PCR-positive/culture-negative (p<0.05). Forty-two women returned for a 3 week test-of-cure (ToC), and 10 (24%) were still TV PCR-positive. Of the women who remained TV PCR-positive at ToC, the median baseline Ct was 26.9 (IQR: 12.5) vs. 29.3 (IQR: 14.8) among those TV PCR-negative at ToC (p=0.52). Among 7 women who remained TV PCR-positive, the median baseline Ct was 26.4 (IQR: 6.7) vs. 26.2 (IQR: 6.7) at ToC (p>0.05).
Conclusion The prevalence of TV in our sample of South African HIV-infected pregnant women was similar to prior studies. At baseline, culture detected only half of the cases that were positive by TV PCR. The culture-negative cases had significantly higher Ct values, indicating a lower burden of TV nucleic acid. Baseline Ct values did not predict response to TV treatment. Among women testing persistently TV PCR-positive, Ct values did not change between baseline and ToC.